1. Field of the Invention
The present invention relates to a control chip of a card reader, and more particularly to the control chip and the detecting method capable of detecting the interference among the memory cards sharing the pins of the card reader.
2. Description of Related Art
Simple designs are preferably used in conventional multiple card readers, among which most adopt respective read/write interfaces for all types of memory cards. Another approach is to provide common pins for the memory cards, reducing the size of an IC package with fewer pins. Nevertheless, only one memory card can be inserted for accessing data at one time, since the interference of the common pins may corrupt data or cause failure when data is being accessed.
Reference is made to FIG. 1, which shows a block diagram of a multiple card reader with respective interfaces for different memory cards. The pin used for a multiple card reader is coupled to a CF card/Micro Drive card read/write interface 11, a SM card/xD-Picture card read/write interface 12, a SD card/MMC card read/write interface 13 and a MS card/MS Pro card read/write interface 14. Since common pins are not adopted in conventional read/write interfaces of the control chip 1, there will be no interference in this case. This design, however, needs more pins for each package and thus more cost.
FIG. 2 shows a block diagram of a multiple card reader adopting common pins for nearly all types of memory cards. The pins of the card reader control chip 2 are jointly used by the CF card/Micro Drive card read/write interface 21, SM card/xD-Picture card read/write interface 22, SD card/MMC card read/write interface 23, and MS card/MS Pro card read/write interface 24. There are several ways to implement such common pins, whereas their purpose is mainly for the sake of reducing cost. Since the interference caused by the common pins are not solved in conventional designs, only one memory card can be inserted for accessing data at one time in conventional multiple card readers. An all-in-one socket may be applied by mechanical limitations so that only one memory card can be inserted at one time.
If the interference is ignored, unexpected results leading to malfunction may occur. For example, if several cards are inserted at the same time, the card reader control chip 2 may fail to access a first memory card if a second memory card is inserted into or pulled out from one of the memory card read/write interfaces. Furthermore, if the incident occurred while the first memory card is undergoing a read/write process, data errors that are read or written may happen due to the interference.
Although the card reader shown in FIG. 2 lessens the package cost and is compatible with many types of the memory cards, the disadvantage that only one memory card can be accepted by the card reader at a time is still a major drawback. This is especially true when at least two memory cards are to be used for transmitting data with other.